Antrax, on 2011-July-26, 03:20, said:
This is from Robson / Segal, right? I started reading it but I think it's too advanced for me at this stage.
I don't remember where I learned it, but it is in there. There's no need to play that way, just play the "simple" way described above. Ignoring the 'how I'd actually play in active competition' bit from my previous post, here's a general rule with a major suit fit that should serve you well:
Below 3 of our major suit, new suit bids show shape and general location of values. Above 3 of our major suit, new suit bids are cuebids. The former may be interested only in trying for game or choice of game or may be showing shape/values with the intent of later trying for slam. The latter shows slam interest.
I mean this completely generally, i.e. even if you're already in a game force. The only exception would be if you already have specified meanings, for example maybe you play specific rebids after Jacoby 2NT. Even so, notice that showing shortness after Jacoby 2NT ties in with the above philosophy: opener is showing shape below 3 of your major, just by showing shortness instead of length.